Breast Cancer

PD 17 - Breast 4 -Poster Discussion

1146 - Postoperative Single-Fraction Partial Breast Irradiation for Low-Risk Stage 0 and I Breast Carcinomas: Results of a Prospective Clinical Trial

Wednesday, October 24
1:42 PM - 1:48 PM
Location: Room 217 A/B

Postoperative Single-Fraction Partial Breast Irradiation for Low-Risk Stage 0 and I Breast Carcinomas: Results of a Prospective Clinical Trial
W. R. Kennedy1, M. A. Thomas1, K. R. DeBroeck1, L. L. Ochoa1, A. R. Atkinson1, O. L. Green2, and I. Zoberi1; 1Washington University School of Medicine, Department of Radiation Oncology, St. Louis, MO, 2Washington University School of Medicine, St. Louis, MO

Purpose/Objective(s): To prospectively evaluate clinical, cosmetic, and quality of life outcomes in women treated with single-fraction high-gradient partial breast irradiation (HG-PBI) after breast-conserving surgery for early-stage breast cancer.

Materials/Methods: Between 2014 and 2017, patients were enrolled in a single-institution prospective phase I/II trial receiving postoperative HG-PBI, 20 Gy to the cavity surface while simultaneously prescribing 7 Gy to a planning target volume (PTV) defined as the surgical bed plus a 1cm margin. MRI-guided radiotherapy was used to deliver treatment in all but two patients. Eligible patients were postmenopausal women aged ≥50 years with hormone receptor positive, HER2/neu nonamplified stage 0 or I breast cancer treated with partial mastectomy with negative histologic margins.

Results: There were 43 patients evaluable. Mean age at diagnosis was 66 years. Median follow-up was 12 months. Patients had stage 0 (10 patients, 23%) or stage 1 (34 patients, 77%) disease. Breast MRI was used during preoperative workup in 30% of patients. On average, the mean PTV volume was 94cc (range 26 – 321cc), mean heart dose was 0.43 Gy (range, 0.07 – 1.52 Gy), and maximum skin rind dose was 17.93 Gy (range, 8.43 – 28.53 Gy). Adjuvant hormone suppression was given after HG-PBI in 76% of patients. Adjuvant chemotherapy was given after HG-PBI in 2 patients (5%). No grade 3-5 toxicities per CTCAE v4.0 were observed. All but one toxicity has been grade 1, with 12 patients having hyperpigmentation in the treatment region and 6 having transient breast pain. One patient experienced grade 2 chest wall pain. There was no detrimental effect of HG-PBI on patient-reported quality of life per EORTC QLQ-30 and QLQ-BR23. The rates of excellent-to-good cosmesis reported by patients and the treating radiation oncologist were 97% and 100% pretreatment, 97% and 100% at 8 weeks follow-up, and 100% and 100% at 6 months, respectively. Quantitative evaluation of cosmesis by percentage of breast retraction assessment (pBRA), showed that compared to pretreatment pBRA (9.07) there was no significant change in pBRA over time. One patient developed ductal carcinoma in situ in a separate quadrant of the ipsilateral breast 18 months after treatment. There were no recurrences in the treated quadrant, regional lymph nodes, or distantly, with no intercurrent deaths observed.

Conclusion: Single fraction HG-PBI was well-tolerated and resulted in few adverse events. Both patients and the treating physicians reported high rates of excellent-to-good cosmetic outcomes. Patient-reported quality of life did not decrease after treatment. Single fraction HG-PBI did not significantly change breast size as measured by pBRA. Early local, regional, and distant control rates were excellent.

Author Disclosure: W.R. Kennedy: None. M.A. Thomas: None. K.R. DeBroeck: None. L.L. Ochoa: None. O.L. Green: Honoraria; ViewRay, Inc. Travel Expenses; ViewRay, Inc. I. Zoberi: Employee; Washington University. Stock; ViewRay.

William Kennedy, MD

Disclosure:
No relationships to disclose.

Biography:
Billy Kennedy, MD is a second-year radiation oncology resident at Washington University in St. Louis. His hometown is in Gainesville, FL. He received his BS in biochemistry from Rollins College in Winter Park, FL. He then earned his MD at the University of Florida College of Medicine, also in Gainesville, FL.

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